A cross-Canada survey has found a potent liver toxin in every province’s lakes, with the highest concentrations in the popular cottage and recreational waters of central Alberta and southern Manitoba.
Although it’s been known for a long time that sewage and agricultural runoff cause water quality problems, new technology has allowed scientists for the first time to isolate and quantify the presence of microcystin, said lead author Diane Orihel.
“As lakes have higher and higher concentrations of nutrients, we see more and more [blue-green algae] and more and more microcystins,” said Ms. Orihel, whose research was published Tuesday.
“We need to get serious about water quality in these lakes. This is now a human health concern across Canada.”
Microcystins are potentially fatal to humans. As well, they are suspected of being carcinogenic at long-term, low exposure.
They are also associated with death and illness in wildlife.
The toxin is produced by some species of cyanobacteria, also known as blue-green algae. Blue-green algae is a common feature of nutrient-rich lakes such as the shallow, warm lakes on the prairies.
Those environments already tend to be naturally rich in nitrogen and phosphorus. In addition, they often receive large amounts of those chemicals in runoff from agricultural fertilizers and manure, as well as sewage from recreational properties.
Ms. Orihel’s research found that when nitrogen exceeded phosphorus by less than a factor of 20 lakes tended to have high levels of microcystins.
Her survey found such conditions in 246 lakes across the country. Every province had lakes where microcystin levels were “of concern.”
Several Alberta lakes between Edmonton and Calgary, where microcystin levels routinely exceeded 10 micrograms per litre, comprised one of the hot spots. Another was in northwestern Alberta and southern Manitoba.
Proposed Canadian guidelines for recreational microcystin exposure – which includes swimming in the water or even inhaling droplets – is 20 micrograms per litre. Ms. Orihel’s survey suggested 9 per cent of the lakes surveyed exceeded that level.
Ms. Orihel said cottagers and boaters should pay close attention to blue-green algae warnings issued by provincial governments. When those levels are high, microcystins are also likely to be high.
More research is needed to nail down the links between algae, nutrients, human activity and microcystins, she said.
“We have a poor understanding of where and when these toxins will appear in our lakes.
“The next step would be to conduct large-scale experiments where we manipulate nitrogen-to-phosphorus ratios. I think that information is critical for developing nutrient management strategies.”
One place where such work would be possible would be the Experimental Lakes Area in Ontario, a unique open-air lab of 58 remote Ontario water bodies that allows scientists to conduct experiments on entire ecosystems. The future of that facility is in doubt after the federal announced last spring that it would cut the $2-million in funding it receives.
“There’s really only one place in the world where you can do work like that and that’s the Experimental Lakes Area,” Ms. Orihel said.
Although she has been heavily involved in the attempt to save the program, Ms. Orihel denies her survey has been released in an attempt to pressure the government. She points out the study was accepted for publication well before news broke about the Tory funding decision.
She’s urging landowners and agricultural producers to take responsibility for the water quality in their own lakes. Improving sewage treatment and restoring natural lakeside vegetation are two moves that would go a long way to reducing microcystin risk, Ms. Orihel suggested.
“They have a role to play in cleaning up their lakes.”
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